The present invention relates generally to a system for recording signals on a record disc. More particularly, it relates to a record disc recording system which limits the level of the amplification of the recording signal, to successively decrease it, as the record cutting progresses from the outer periphery toward the inner part of a disc.
In general, the difference between relative linear velocity of a disc rotating at a constant rotational speed and a pickup cartridge reproducing signals from the disc differs at the outer peripheral part and the inner part of the record because of the difference in their radii. The tracing state of the pickup cartridge, relative to the disc, becomes worse as the cartridge moves, from the outer periphery toward the inner part thereof.
Particularly consider a case where the recorded program is a symphony or the like, for example, having a loud climax in the finale. This finale is recorded on the inner part of the disc where tracing distortion increases and greatly impairs the reproduced tone quality.
Furthermore, consider a multichannel record disc of a discrete system which applicant has previously developed and which is being widely used. An angle-modulated wave and a direct wave signal are recorded on the disc in a multiplexed state. Accordingly, as the pickup cartridge advances toward the inner part of the disc, and the distortion increases as described above, there is also the possibility of the higher harmonics of the direct wave signal entering the angle-modulated wave band to give rise to cross modulation or overmodulation and abnormal noises.
In order to solve this problem, it has been the conventional practice either to lower the entire level of the recording signal or to use a limiting amplifier for automatic gain control with respect to the recording signal. This amplifier is set so that the gain control will be carried out in a large extent.
All of these conventional measures, however, have been accompanied by difficulties such as the loss of the sensation of sound volume over the entire program. Small dynamic range at the time of recording due to an even lowering of the recording signal level as the recording progresses from the outer periphery to the inner periphery of the disc. Or, there is a suppressing of the maximum levels below a relatively low specific level.